The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based ther...The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.展开更多
The machining principle and realization method for the continuous generative grinding face gear by a worm wheel are introduced. Based on a five-axis linked CNC grinding machine, a new method is presented to deprive th...The machining principle and realization method for the continuous generative grinding face gear by a worm wheel are introduced. Based on a five-axis linked CNC grinding machine, a new method is presented to deprive the equation of face gear error tooth surface by assuming the tool surface as the error surface, where actual tool installation position error is introduced into the equation of virtual shaper cutter. Surface equations and 3-D models for the face gear and the worm wheel involving four kinds of tool installation errors are established. When compared, the face gear tooth surface machined in VERICUT software for simulation based on this new method and the one obtained based on real process(grinding face gear by using a theoretical worm wheel with actual position errors) are found to be coincident, which proves the validity and feasibility of this new method. By using mesh planning for the rotating projection plane of the face gear work tooth surface, the deviation values of the tooth surface and the difference surface are acquired, and the influence of four kinds of errors on the face gear tooth surface is analyzed. Accordingly, this work provides a theoretical reference for assembly craft of worm wheel, improvement of face gear machining accuracy and modification of error tooth surface.展开更多
In asymmetric conditions,the movement and loads of left/right wheels or front/back wheels of the aircraft with multi-wheel or four-wheel bogie landing gears are inconsistent.There are few open literatures related to a...In asymmetric conditions,the movement and loads of left/right wheels or front/back wheels of the aircraft with multi-wheel or four-wheel bogie landing gears are inconsistent.There are few open literatures related to anti-skid braking system for multi-wheels due to technology blockade.In China,the research on multi-channel control and non-equilibrium regulation has just started,and the design of multi-channel control system for anti-skid braking,the simulation of asymmetry taxiing under braking are not studied.In this paper,a dynamics model of ground movement for aircraft with four-wheel bogie landing gears is established for braking simulation, considering the six-degree-of-freedom aircraft body and the movement of bogies and wheels.A multi-channel anti-skid braking system is designed for the wheels of the main landing gears with four-wheel bogies.The eight wheels on left and right landing gears are divided into four groups,and each group is controlled via one channel.The cross protection and self-locked protection modules are added between different channels.A multi-channel anti-skid braking system with slip-ratio control or with slip-velocity control is established separately.Based on the aircraft dynamics model,aircraft braking to stop with anti-skid control on dry runway and on wet runway are simulated.The simulation results demonstrate that in asymmetric conditions,added with cross protection and self-locked protection modules,the slip-ratio-controlled braking system can automatically regulate brake torque to avoid deep slipping and correct aircraft course.The proposed research has reference value for improving brake control effect on wet runway.展开更多
In order to improve the machining efficiency of the dish wheel grinding face gear, two changes are proposed:a disk wheel grinding face gear with a long radius and a multi-axis movement optimization method for tooth su...In order to improve the machining efficiency of the dish wheel grinding face gear, two changes are proposed:a disk wheel grinding face gear with a long radius and a multi-axis movement optimization method for tooth surface correction. Based on the grinding principle of face gears, the equation of the long radius disk wheel is deduced. Based on the structure of the machining tool, the tooth surface equations of the face gear shaped by the long radius disk wheel are established. Furthermore, an optimization model of face gear tooth surface correction is established, and the machine tool motion optimization of face gear tooth surface correction is completed;Finally, a long radius disk wheel grinding face gear test is performed. After the face gear tooth surface correction, the maximum value of the tooth surface deviation is reduced from 180 μm to 16 μm which verified the correctness of the machining method.展开更多
The YM7132A gear grindingmachine with a conical grindingwheel is used for grindingcylindrical spur and helical involutegears,especially for hardenedprecision gears of small andmedium sizes.
The machine is used for precisiongrinding of hardened cylindricalgears with medium module inbatches for the industries ofaircraft,automobile,machine tool,gear box and various transmissiondevices.
The YK7250 gear grinding machine with worm grinding wheel is manufactured by the Qinchuan Machine Tool Group Co., Ltd. in Baoji City, Shaanxi Province.
As all-electric aircraft has many advantages,an aircraft nose wheel steering system would be developed to the all-electric direction.Concerning the control demand of the nose wheel steering system,based on the basic p...As all-electric aircraft has many advantages,an aircraft nose wheel steering system would be developed to the all-electric direction.Concerning the control demand of the nose wheel steering system,based on the basic principles of nose wheel steering system and the design technique of mechanotronics,an all-electric aircraft nose wheel steering system,composed of a nose wheel steering mechanism of two worm gear and a control servo system of fly-by-wire with both steering and anti-shimmy functions is designed to meet the demand for operation control in the nose wheel steering system.Then,based on the LMS-AMESim software,the simulation model of the system is established to simulate the dynamics for the verification of its steering function.The simulation results indicate that the nose wheel steering system is reasonable,and can meet the requirements of the general project.Furthermore,the prototypes of the steering mechanism and control system are studied to validate the design,and the steering test bench is prepared to test the designed system.The test results,such as steer angle,rotate speed of motor are analyzed in details and compared with the theoretical results.The analysis and comparison results show that the design is reasonable and the property of the prototype can achieve the design objectives.展开更多
The manufacturing accuracy of ultra-precision master gears signifies the technological capability of the ultra-precision gear.Currently,there is little report about the manufacturing technologies of ultra-precision ma...The manufacturing accuracy of ultra-precision master gears signifies the technological capability of the ultra-precision gear.Currently,there is little report about the manufacturing technologies of ultra-precision master gears at home and aboard.In order to meet the requirement of grinding ultra precision master gear,the gear grinder with flat-faced wheel Y7125 is chosen as the object machine tool and the geometric model of its precision generating part,the involute cam,is established.According to the structure of the involute cam,the effective working section and its adjustable range of the cam are determined,and the mathematical expressions of the effects of comprehensive eccentricity of the involute cam on gear profile deviations are derived.According to the primary harmonic trends of the deviation curve,it is shown that gear profile form and slope deviations in different work generating sections of the involute cam are different which the latter changes with the cam eccentricity obviously.Then,the issues of extreme values and methods of error compensation are studied and the conclusion that large adjustable range is benefit to search the optimal involute-cam section which is responding to the minimum gear profile deviations is obtained.A group of examples are calculated by choosing master gears with d=120 mm and m=2-6 mm and an involute cam with base diameter djcam =117 mm.And it is found that the maximum gear profile deviation counts for no more than 5% of the cam eccentricity after error compensation.A gear-grinding experiment on the master gear with m=2 mm is conducted by choosing different sections of the involute cam and the differences of gear profile deviations then the existence of the cam eccentricity are verified.The research discloses the rule of gear profile deviations caused by the comprehensive eccentricity of the involute cam and provides the theoretical guidance and the processing methods for grinding profile of the ultra precision master gear.展开更多
基金This study was financially supported by the Major State Basic Research Development Program of China (No.2004CB719802)the National High-Tech Research and Development Program of China (No.2006aa03Z113)the Program of the Ministry of Educa-tion of China for Changjiang Scholars and Innovative Research Team in Universities (No.I2P407).
文摘The micropowder injection molding technology was investigated to fabricate the microsized gear wheels on a conventional injection molding machine. The feedstock comprised of carbonyl ferrum powder and a wax-based thermoplastic binder. Microinjection molding was fulfilled at about 423 K under 100 MPa. The heating system was applied to the die to improve the fluidity of the feedstock and subsequently the cooling system was used to enhance the strength of the green compacts after injection by decreasing the temperature of the die. The gear wheels were realized successfully with their addendum circle diameter ranging from 800 to 200 um and with the center hole as small as 60 um.
基金Projects(51535012,U1604255)supported by the National Natural Science Foundation of ChinaProject(2016JC2001)supported by the Key Research and Development Project of Hunan Province,China
文摘The machining principle and realization method for the continuous generative grinding face gear by a worm wheel are introduced. Based on a five-axis linked CNC grinding machine, a new method is presented to deprive the equation of face gear error tooth surface by assuming the tool surface as the error surface, where actual tool installation position error is introduced into the equation of virtual shaper cutter. Surface equations and 3-D models for the face gear and the worm wheel involving four kinds of tool installation errors are established. When compared, the face gear tooth surface machined in VERICUT software for simulation based on this new method and the one obtained based on real process(grinding face gear by using a theoretical worm wheel with actual position errors) are found to be coincident, which proves the validity and feasibility of this new method. By using mesh planning for the rotating projection plane of the face gear work tooth surface, the deviation values of the tooth surface and the difference surface are acquired, and the influence of four kinds of errors on the face gear tooth surface is analyzed. Accordingly, this work provides a theoretical reference for assembly craft of worm wheel, improvement of face gear machining accuracy and modification of error tooth surface.
基金supported by National Natural Science Foundation of China (Grant No.51075203)Nanjing University of Aeronautics and Astronautics Research Funding(Grant No.NS2010033)
文摘In asymmetric conditions,the movement and loads of left/right wheels or front/back wheels of the aircraft with multi-wheel or four-wheel bogie landing gears are inconsistent.There are few open literatures related to anti-skid braking system for multi-wheels due to technology blockade.In China,the research on multi-channel control and non-equilibrium regulation has just started,and the design of multi-channel control system for anti-skid braking,the simulation of asymmetry taxiing under braking are not studied.In this paper,a dynamics model of ground movement for aircraft with four-wheel bogie landing gears is established for braking simulation, considering the six-degree-of-freedom aircraft body and the movement of bogies and wheels.A multi-channel anti-skid braking system is designed for the wheels of the main landing gears with four-wheel bogies.The eight wheels on left and right landing gears are divided into four groups,and each group is controlled via one channel.The cross protection and self-locked protection modules are added between different channels.A multi-channel anti-skid braking system with slip-ratio control or with slip-velocity control is established separately.Based on the aircraft dynamics model,aircraft braking to stop with anti-skid control on dry runway and on wet runway are simulated.The simulation results demonstrate that in asymmetric conditions,added with cross protection and self-locked protection modules,the slip-ratio-controlled braking system can automatically regulate brake torque to avoid deep slipping and correct aircraft course.The proposed research has reference value for improving brake control effect on wet runway.
基金Supported by Key Project of Advanced Research Foundation(9140A18020113)Advanced Research Foundation Project(9140A18020212)+1 种基金Advanced Research Project(51318025131812)
文摘In order to improve the machining efficiency of the dish wheel grinding face gear, two changes are proposed:a disk wheel grinding face gear with a long radius and a multi-axis movement optimization method for tooth surface correction. Based on the grinding principle of face gears, the equation of the long radius disk wheel is deduced. Based on the structure of the machining tool, the tooth surface equations of the face gear shaped by the long radius disk wheel are established. Furthermore, an optimization model of face gear tooth surface correction is established, and the machine tool motion optimization of face gear tooth surface correction is completed;Finally, a long radius disk wheel grinding face gear test is performed. After the face gear tooth surface correction, the maximum value of the tooth surface deviation is reduced from 180 μm to 16 μm which verified the correctness of the machining method.
文摘The YM7132A gear grindingmachine with a conical grindingwheel is used for grindingcylindrical spur and helical involutegears,especially for hardenedprecision gears of small andmedium sizes.
文摘The machine is used for precisiongrinding of hardened cylindricalgears with medium module inbatches for the industries ofaircraft,automobile,machine tool,gear box and various transmissiondevices.
文摘The YK7250 gear grinding machine with worm grinding wheel is manufactured by the Qinchuan Machine Tool Group Co., Ltd. in Baoji City, Shaanxi Province.
基金supported partly by the Aeronautical Science Foundation of China(No.20142852025)
文摘As all-electric aircraft has many advantages,an aircraft nose wheel steering system would be developed to the all-electric direction.Concerning the control demand of the nose wheel steering system,based on the basic principles of nose wheel steering system and the design technique of mechanotronics,an all-electric aircraft nose wheel steering system,composed of a nose wheel steering mechanism of two worm gear and a control servo system of fly-by-wire with both steering and anti-shimmy functions is designed to meet the demand for operation control in the nose wheel steering system.Then,based on the LMS-AMESim software,the simulation model of the system is established to simulate the dynamics for the verification of its steering function.The simulation results indicate that the nose wheel steering system is reasonable,and can meet the requirements of the general project.Furthermore,the prototypes of the steering mechanism and control system are studied to validate the design,and the steering test bench is prepared to test the designed system.The test results,such as steer angle,rotate speed of motor are analyzed in details and compared with the theoretical results.The analysis and comparison results show that the design is reasonable and the property of the prototype can achieve the design objectives.
基金supported by National Hi-tech Research and Development Program of China (863 Program,Grant No.2008AA042506)
文摘The manufacturing accuracy of ultra-precision master gears signifies the technological capability of the ultra-precision gear.Currently,there is little report about the manufacturing technologies of ultra-precision master gears at home and aboard.In order to meet the requirement of grinding ultra precision master gear,the gear grinder with flat-faced wheel Y7125 is chosen as the object machine tool and the geometric model of its precision generating part,the involute cam,is established.According to the structure of the involute cam,the effective working section and its adjustable range of the cam are determined,and the mathematical expressions of the effects of comprehensive eccentricity of the involute cam on gear profile deviations are derived.According to the primary harmonic trends of the deviation curve,it is shown that gear profile form and slope deviations in different work generating sections of the involute cam are different which the latter changes with the cam eccentricity obviously.Then,the issues of extreme values and methods of error compensation are studied and the conclusion that large adjustable range is benefit to search the optimal involute-cam section which is responding to the minimum gear profile deviations is obtained.A group of examples are calculated by choosing master gears with d=120 mm and m=2-6 mm and an involute cam with base diameter djcam =117 mm.And it is found that the maximum gear profile deviation counts for no more than 5% of the cam eccentricity after error compensation.A gear-grinding experiment on the master gear with m=2 mm is conducted by choosing different sections of the involute cam and the differences of gear profile deviations then the existence of the cam eccentricity are verified.The research discloses the rule of gear profile deviations caused by the comprehensive eccentricity of the involute cam and provides the theoretical guidance and the processing methods for grinding profile of the ultra precision master gear.
